Solution-processable, soft, self-adhesive, and conductive polymer composites for soft electronics

Abstract

Soft electronics are rising electronic technologies towards applications spanning from healthcare monitoring to medical implants. However, poor adhesion strength and significant mechanical mismatches inevitably cause the interface failure of devices. Herein we report a self-adhesive conductive polymer that possesses low modulus (56.1-401.9 kPa), high stretchability (700%), high interfacial adhesion (lap-shear strength >1.2 MPa), and high conductivity (1-37 S/cm). The self-adhesive conductive polymer is fabricated by doping the poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) composite with a supramolecular solvent (β-cyclodextrin and citric acid). We demonstrated the solution process-based fabrication of self-adhesive conductive polymer-based electrodes for various soft devices, including alternating current electroluminescent devices, electromyography monitoring, and an integrated system for the visualization of electromyography signals during muscle training with an array of alternating current electroluminescent devices. The self-adhesive conductive polymer-based electronics show promising features to further develop wearable and comfortable bioelectronic devices with the physiological electric signals of the human body readable and displayable during daily activities.

Reversible Wet‐Adhesive and Self‐Healing Conductive Composite Elastomer of Liquid Metal

“…The results reveal that the performance of the adhesive and conductive elastomer electrode is comparable to the commercial electrode (Figure S26, Supporting Information) and the other conductive materials in literatures. [43][44][45] By applying 0, 0.5, and 1.5 kg of lifting forces, the composite LM electrode can monitor the steady increase of the EMG signals (Figure S27, Supporting Information). In addition, the EMG signals do not show significant attenuation even when the composite LM electrodes had been used ten times (Figure 5E; Figure S28, Supporting Information).…”

Anti-Freezing, Non-Drying, Localized Stiffening, and Shape-Morphing Organohydrogels

“…Although the present study demonstrates the design of a programmable shape-morphing system with tough organohydrogels and the utility of this material for packaging of functional components with different elastic moduli, the core strategy and the as-developed technology platform can be employed for a wide range of applications with extended conditions in challenging environments. For example, our strategy has implications towards the bio-inspired design of human–machine/machine–machine interfaces [ 33 ], soft robotics [ 51 ], sensors [ 52 ], soft electronics [ 53 ], and actuators [ 20 , 22 ], with a particular focus on locally tunable mechanical properties and working under more challenging environments.…”

Application of conductive polymer hydrogels in flexible electronics

“…The CPH prepared by mixing citric acid (H 3 Cit), glutaraldehyde (GA), cyclodextrin (CD), PVA and PEDOT:PSS have a high conductivity of 37 S cm −1 and a strong interfacial bonding strength (Figure 2C). 122 The CPH has been demonstrated for applications including alternating current electroluminescent (ACEL) devices and adhesive bioelectrodes for electromyography (EMG) monitoring. In addition, CPH with PVA as a hydrogel matrix can be easily prepared by direct polymerization through a cyclic freeze–thaw process.…”

“…An acid‐treated PEDOT:PSS hydrogel suspension was reported by Yao et al 110 The hydrogel, with a solid content of only 4%, can be fabricated into different shapes such as thin films, fibers and columns with arbitrary sizes for practical applications (Figure 5A). Tan et al 122 report a self‐adhesive PEDOT: PSS hydrogel, which can be processed by various solution‐processing techniques (such as microfluidic molding, droplet casting and spin coating) owing to its excellent stability, homogeneity, and “coffee ring” free patterning capability (Figure 5B). The CPH can be deposited in microchannels to form “U” shaped films, or patterned films can be formed on Ecoflex substrates using droplet casting and laser patterning techniques.…”

“…The patterned films on Ecoflex substrates did not delaminate under repeated stretching, indicating the high adhesion stability of hydrogels on soft dynamic surfaces. It can also be used as transparent electrodes by spin coating in optoelectronic devices 122 . In addition, CPHs can be formed into micropatterns by inkjet printing or 3D printing.…”